1. Field of the Invention
The present invention relates to a coupling device and a method of manufacturing a coupling device, and more particularly, it relates to a coupling device including a magnet rotator and a yoke-side member coupled to the magnet rotator and a method of manufacturing a coupling device.
2. Description of the Background Art
A coupling device including a magnet rotator and a yoke-side member coupled to the magnet rotator is known in general, as disclosed in Japanese Patent Laying-Open No. 8-135682 (1996), for example.
Japanese Patent Laying-Open No. 8-135682 discloses a starting device (coupling device) including a discoidal (disk-shaped) driving member (magnet rotator) including a plurality of permanent magnets so arranged that different magnetic poles alternately line up in a circumferential direction and a discoidal driven member (yoke-side member) arranged to be opposed to the permanent magnets of the driving member. The driven member of the starting device described in Japanese Patent Laying-Open No. 8-135682 is constituted of a conductive member (conductor portion) provided with a plurality of through-holes on positions opposed to the permanent magnets and a core member (yoke), having projecting portions corresponding to the through-holes, arranged on a side of the conductive member opposite to the driving member. The core member passes through the through-holes of the conductive member so that end surfaces of the projecting portions approach the permanent magnets, thereby increasing the amount of magnetic flux passing through the projecting portions (through-holes) of the core member. Thus, the amount of eddy current flowing in the conductive member is so increased that a relatively high torque can be generated in the driven member. In order to generate a higher torque in the driven member, the amount of generated eddy current must conceivably be increased by increasing the areas of portions of the driving member and the driven member opposed to each other.
In the starting device disclosed in Japanese Patent Laying-Open No. 8-135682, however, both of the driving member and the driven member are discoidal, and hence the sizes of the discoidal driving member and the discoidal driven member must be both radially increased in order to increase the areas of the portions of the driving member and the driven member opposed to each other. Therefore, the size of the starting device disclosed in Japanese Patent Laying-Open No. 8-135682 is disadvantageously radially increased due to the radial increase of the sizes of the discoidal driving member and the discoidal driven member.